Image forming apparatus and belt transport device having a cleaning mechanism

Abstract

An image forming apparatus includes: an image forming unit forming a toner image; an image carrier carrying the toner image; an endless transfer belt rotating with a recording medium interposed between the transfer belt and the image carrier; a cleaner provided in contact with an outer surface of the transfer belt and electrostatically cleaning toner on the outer surface; a transfer roll provided inside the transfer belt and generating a transfer electric field for transferring the toner image from the image carrier to the recording medium while pressing the transfer belt toward the image carrier; a cleaning roll mounted around by the transfer belt as well as the transfer roll, the cleaning roll provided to face the cleaner and generating a cleaning electric field; and a tension roll mounted around by the transfer belt as well as the transfer roll and the cleaning roll.

What is claimed is: 
     
       1. An image forming apparatus comprising:
 an image forming unit that forms a toner image; 
 an image carrier that carries the toner image formed by the image forming unit; 
 a transfer belt that is endless and rotates with a recording medium interposed between the transfer belt and the image carrier; 
 a cleaner that is provided to be in contact with an outer surface of the transfer belt and electrostatically cleans toner adhering to the outer surface of the transfer belt; 
 a transfer roll that is provided inside the transfer belt and generates a transfer electric field between the transfer roll and the image carrier for transferring the toner image from the image carrier to the recording medium while pressing the transfer belt toward the image carrier; 
 a cleaning roll which is mounted proximate to the transfer belt as well as the transfer roll, the cleaning roll being provided to face the cleaner; and 
 a tension roll which is mounted proximate to the transfer belt as well as the transfer roll and the cleaning roll, wherein
 a diameter of the cleaning roll is larger than a diameter of the tension roll. 
 
 
     
     
       2. The image forming apparatus according to  claim 1 , wherein
 the tension roll is provided downstream of the transfer roll in a rotation direction of the transfer belt, and 
 a diameter of the tension roll is smaller than a diameter of the transfer roll. 
 
     
     
       3. An image forming apparatus comprising:
 an image forming unit that forms a toner image; 
 an image carrier that carries the toner image formed by the image forming unit; 
 a transfer belt that is endless and rotates with a recording medium interposed between the transfer belt and the image carrier; 
 a cleaner that is provided to be in contact with an outer surface of the transfer belt and electrostatically cleans toner adhering to the outer surface of the transfer belt; 
 a transfer roll that is provided inside the transfer belt and generates a transfer electric field between the transfer roll and the image carrier for transferring the toner image from the image carrier to the recording medium while pressing the transfer belt toward the image carrier; 
 a cleaning roll which is mounted proximate to the transfer belt as well as the transfer roll, the cleaning roll being provided to face the cleaner; and 
 a tension roll which is mounted proximate to the transfer belt as well as the transfer roll and the cleaning roll, wherein
 a diameter of the cleaning roll is larger than a diameter of the tension roll, 
 the cleaner includes a first cleaning member and a second cleaning member, to which voltages of mutually different polarities are applied, each of the first cleaning member and the second cleaning member cleaning the transfer belt, 
 the first cleaning member is provided in contact with a surface of the transfer belt between the cleaning roll and the transfer roll, and 
 the second cleaning member is provided in contact with a surface of the transfer belt between the cleaning roll and the tension roll. 
 
 
     
     
       4. The image forming apparatus according to  claim 3 , wherein
 the tension roll is provided downstream of the transfer roll in a rotation direction of the transfer belt, and 
 a diameter of the tension roll is smaller than a diameter of the transfer roll. 
 
     
     
       5. An image forming apparatus comprising:
 an image forming unit that forms a toner image; 
 an image carrier that carries the toner image formed by the image forming unit; 
 a transfer belt that is endless and rotates with a recording medium interposed between the transfer belt and the image carrier; 
 a cleaner that is provided to be in contact with an outer surface of the transfer belt and electrostatically cleans toner adhering to the outer surface of the transfer belt; 
 a transfer roll that is provided inside the transfer belt and generates a transfer electric field between the transfer roll and the image carrier for transferring the toner image from the image carrier to the recording medium while pressing the transfer belt toward the image carrier; 
 a cleaning roll which is mounted proximate to the transfer belt as well as the transfer roll, the cleaning roll being provided to face the cleaner; and 
 a tension roll which is mounted proximate to the transfer belt as well as the transfer roll and the cleaning roll, wherein
 a diameter of the cleaning roll is larger than a diameter of the tension roll, 
 the cleaner includes a first cleaning member and a second cleaning member, to which voltages of mutually different polarities are applied, each of the first cleaning member and the second cleaning member cleaning the transfer belt, 
 the first cleaning member is provided in contact with a surface of the transfer belt between the cleaning roll and the transfer roll, 
 the second cleaning member is provided in contact with a surface of the transfer belt between the cleaning roll and the tension roll, 
 the first cleaning member and the second cleaning member in the cleaner are positioned in a region between a first virtual line segment and a second virtual line segment, the first virtual line segment extending vertically downward from an upstream side end portion of a belt surface in a moving direction of the transfer belt, the second virtual line segment extending vertically downward from a downstream side end portion of the belt surface in the moving direction of the transfer belt, and 
 the belt surface being provided between the transfer roll and the tension roll. 
 
 
     
     
       6. The image forming apparatus according to  claim 5 , wherein
 the tension roll is provided downstream of the transfer roll in a rotation direction of the transfer belt, and 
 a diameter of the tension roll is smaller than a diameter of the transfer roll. 
 
     
     
       7. An image forming apparatus comprising:
 an image forming unit that forms a toner image; 
 an image carrier that carries the toner image formed by the image forming unit; 
 a transfer belt that is endless and rotates with a recording medium interposed between the transfer belt and the image carrier; 
 a cleaner that is provided to be in contact with an outer surface of the transfer belt and electrostatically cleans toner adhering to the outer surface of the transfer belt; 
 a transfer roll that is provided inside the transfer belt and generates a transfer electric field between the transfer roll and the image carrier for transferring the toner image from the image carrier to the recording medium while pressing the transfer belt toward the image carrier; 
 a cleaning roll which is mounted proximate to the transfer belt as well as the transfer roll, the cleaning roll being provided to face the cleaner and generating a cleaning electric field between the cleaning roll and the cleaner; and 
 a tension roll which is mounted proximate to the transfer belt as well as the transfer roll and the cleaning roll, 
 wherein the tension roll is provided downstream of the transfer roll in a rotation direction of the transfer belt, 
 a diameter of the tension roll is smaller than a diameter of the transfer roll, and 
 a diameter of the cleaning roll is larger than the diameter of the tension roll. 
 
     
     
       8. The image forming apparatus according to  claim 7 , wherein
 the cleaner includes a first cleaning member and a second cleaning member, to which voltages of mutually different polarities are applied, each of the first cleaning member and the second cleaning member cleaning the transfer belt, 
 the first cleaning member is provided in contact with a surface of the transfer belt between the cleaning roll and the transfer roll, and 
 the second cleaning member is provided in contact with a surface of the transfer belt between the cleaning roll and the tension roll. 
 
     
     
       9. The image forming apparatus according to  claim 8 , wherein
 the first cleaning member and the second cleaning member in the cleaner are positioned in a region between a first virtual line segment and a second virtual line segment, the first virtual line segment extending vertically downward from an upstream side end portion of a belt surface in a moving direction of the transfer belt, the second virtual line segment extending vertically downward from a downstream side end portion of the belt surface in the moving direction of the transfer belt, and 
 the belt surface being provided between the transfer roll and the tension roll. 
 
     
     
       10. A belt transport device comprising:
 a transfer belt that is endless and rotates with a recording medium interposed between the transfer belt and an image carrier when the transfer belt is attached to an image forming apparatus including an image forming unit and the image carrier that carries a toner image formed by the image forming unit; 
 a cleaner that is provided to be in contact with an outer surface of the transfer belt and electrostatically cleans toner adhering to the outer surface of the transfer belt; 
 a transfer roll that is provided inside the transfer belt and generates a transfer electric field between the transfer roll and the image carrier of the image forming apparatus for transferring the toner image from the image carrier to the recording medium; 
 a cleaning roll which is mounted proximate to the transfer belt as well as the transfer roll, the cleaning roll being provided to face the cleaner and generating a cleaning electric field between the cleaning roll and the cleaner; and 
 a tension roll which is mounted proximate to the transfer belt as well as the transfer roll and the cleaning roll, wherein 
 the tension roll is provided downstream of the transfer roll in a rotation direction of the transfer belt, 
 a diameter of the tension roll is smaller than a diameter of the transfer roll, and 
 a diameter of the cleaning roll is larger than the diameter of the tension roll.